Known processes for chemically synthesizing optically active (R)-(-)-3-halo-1,2-propanediols include a process starting with D-mannitol, as disclosed in JP-A-57-165352 (corresponding to U.S. Pat. No. 4,413,142), and a process starting with methyl-5-chloro-5-deoxy-.alpha.-L-arabinofuranoside, as disclosed in Chemistry and Industry, Jul. 15, 1978, p. 533. These chemical techniques, however, involve complicated procedures and have many problems when carried out on an industrial scale. On the other hand, known biological techniques include a process comprising allowing a microorganism to act on racemic (R,S)-3-halo-1,2-propanediol to selectively metabolize the (S)-(+)-3-halo-1,2-propanediol while retaining the (R)-(-)-3-halo-1,2-propanediol, as disclosed in JP-A-62-158494, and a process comprising allowing a microorganism belonging to the genus Pseudomonas to act on racemic (R,S)-2,3-dichloro-1-propanol to collect (R)-(-)-3-chloro-1,2-propanediol, as disclosed in JP-A-62-69993. However, these biological processes are not economically advantageous because, as a result of the nature of racemate resolution, the molar yield of the desired (R)-(-)-3-halo-1,2-propanediol based on the starting material is only 50% at the highest.